1. Field of the Invention
The present invention relates to a semiconductor device, more particularly to a semiconductor integrated circuit having a logic verifying structure capable of detecting internal logic states by irradiating a laser beam on the back of the semiconductor integrated circuit having logic circuits constituted by CMOS (Complimentary Metal Oxide Semiconductor) structure, and to a method of manufacturing the semiconductor integrated circuit.
2. Description of the Related Art
There have proposed test systems for detecting internal logic states of a CMOS LSI (Large Scale Integrated Circuit) with non-contacts arranged on the LSI: a system analyzes secondary electrons generated from wiring of the LSI by irradiating an electron beam on the wiring; another system detects an electron beam excitation current generated from a logic of pn junction portions of a semiconductor device for use in an electronic circuit by irradiating an electron beam referred to as an EBIC (Electron Beam Induced Current) on the pn junction; and still another system detects a photo current generated from a logic of a pn junction portion of a semiconductor device for use in an electronic circuit by irradiating a laser beam referred to as an OBIC (Optical Beam Induced Current) on the pn junction.
Since the electron beam should be irradiated on a measuring sample in a space maintained under high vacuum, equipment cost is necessarily high.
Moreover, since a space maintained under high vacuum has physical limitations, the size of the LSI circuit to be measured and the number of input and output terminals are also limited. In contrast, since the laser beam used by the OBIC system can be used in the air, there is no limitation to use a specifically designed electron beam equipment and an LSI to be measured. To this end, the OBIC system for detecting internal logic states in the non-contact has been attracted considerably attention.
Such system has proposed in detail by "Logic Failure Analysis of CMOS LSI Using a Laser Probe", F. J. Henley, IEEE Proceedings of the International Reliability Physics Symposium, 1984, pp 60.BECAUSE.75.
Concerning the OBIC system, a system referred to as back OBIC has been proposed which detects a photo current generated from a logic of pn junction portion by irradiating a laser light on the pn junction portion from the back of a semiconductor substrate opposite to a plane on which an electronic circuit is formed, which has been turned to practical use. Such system has proposed in detail by "the back OBIC Scanner" published by Katsuhide UEDA and Kenji HARADA, LSI Testing Symposium, the minutes in 1996, pp 164-169.